<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    #div1{
      width:400px;
      height:400px;
      background:white;
    }
    body{
      margin:0;
      background: black;
    }
  </style>
</head>
<body>
<div id="div1">
  <svg xmlns="http://www.w3.org/2000/svg" width="100%" height="100%">
    <!--<circle cx="100" cy="100" r="40" fill="red" stroke="black" stroke-width="5"></circle>
    <circle cx="100" cy="100" r="30" fill="red" stroke="black" stroke-width="5"></circle>
    <circle cx="100" cy="100" r="20" fill="red" stroke="black" stroke-width="5"></circle>
    <circle cx="100" cy="100" r="10" fill="red" stroke="black" stroke-width="5"></circle>-->

    <!-- g标签上可以为其内的标签设置一些默认属性 -->
    <!-- g标签里可以是任何图形,So g标签上只能设置一些所有图形共享的属性,比如这里的cx、cy就不会生效 但stroke-width、stroke生效了 -->
    <!--<g cx="200" cy="200" stroke-width="5" stroke="black">
      <circle r="40" fill="red"></circle>
      <circle r="30" fill="red"></circle>
      <circle r="20" fill="red"></circle>
      <circle r="10" fill="red"></circle>
    </g>-->

    <!-- 虽然cs,cy因为不是公有属性,设置在g上无效,但我们可以这样: -->
    <g transform="translate(200,200)" stroke-width="5" stroke="black">
      <circle r="40" fill="red"></circle>
      <circle r="30" fill="red"></circle>
      <circle r="20" fill="red"></circle>
      <circle r="10" fill="red"></circle>
    </g>
  </svg>
</div>
</body>
</html>
